Bollworm complex

The first sign is round bore-holes in the cotton bolls (the pods that hold the lint and seed), or in the pods and fruit of beans, cowpeas, tomatoes, peppers and okra — usually with wet, crumbly droppings (frass) pushed out at the hole. Buds, squares (the flower buds) and young bolls or pods drop off the plant, and if you cut one open the inside is hollow, stained or rotten.

a caterpillar feeding with its head buried inside the boll, pod or fruit and its back half sticking out. No other pest sits like that. One worm will leave a trail of several bored, ruined fruits as it moves along.

(the main one): up to 3-4 cm long — about the length of your thumb from the tip to the first knuckle. Its colour varies a LOT (green, yellow, pink, brown, even almost black), but it always has pale wavy stripes running along the sides with a darker line down the back, and rough, bristly skin that feels like fine sandpaper if you run a finger along it. The head is dark.

are laid one at a time — NOT in a fuzzy mass. Each is tiny, round and dome-shaped like a miniature helmet, white at first and turning brown, stuck on flowers, growing tips and young fruit. Finding single eggs like this is your earliest warning.

the spiny bollworm bores into the growing tip first, so the shoot wilts and droops like a bent candle before you ever see fruit damage. The pink bollworm is small and hides inside the boll, twisting the flower into a bunched "rosette" that never opens properly — cut a suspect boll open to find it.

Armyworms and loopers chew the leaves; bollworm goes for the fruit and pods and bores in. A looper arches its back into a loop as it walks — bollworm crawls flat. If the caterpillar is eating leaves and not boring into fruit, it is not bollworm.

— that is when the moths arrive to lay. Keep checking twice a week right through flowering and boll/pod-fill, because that whole fruiting stretch is the window the worms attack. There is no need to scout for it at the seedling stage.

so you cover all four corners and the middle — not just the edge by the path. Stop at about 5 points, and at each stop check 4-5 plants (about 20-25 plants in all).

the growing tips (for the drooping "candle" shoot and eggs), the squares, buds and open flowers (open a flower and look inside), and the young bolls, pods and fruit. Look for single dome-shaped eggs, tiny caterpillars, and fresh boreholes with frass. Also glance at the ground for shed buds and pods.

treat when about 1 in every 4 plants (roughly 2-3 in every 10) is carrying eggs or young caterpillars, OR when about 5 to 10 out of every 100 fruiting bodies — that is 1 in every 10 to 1 in every 20 squares, bolls or pods — shows a fresh borehole. Below that, keep watching; do not spray.

A fresh, moist hole with soft frass means a worm is still working — act on it. An old, dry hole with no worm inside is past damage — do not spend a spray on it.

— a small lure trap that gives off the female moth's scent and catches the male moths. A sudden jump in the nightly catch warns you that egg-laying is about to start, so you know to scout harder and to time any spray to hit the new eggs and young worms.

Only if scouting reaches the threshold. A pyrethroid is a contact poison — it kills only the worm the spray actually touches, so aim it at the exposed eggs and young worms before they bore in. SAFETY: cover your skin, eyes, nose and mouth; spray in the cool of early morning or evening with the wind at your back; keep it off food, drinking water, children, animals and bees; respect the pre-harvest interval (the number of days the label says you must wait between the last spray and picking, so no poison is left on what you eat or sell); and wash yourself and the sprayer afterwards. RESISTANCE: bollworms quickly become immune to pyrethroids if you use them again and again — so spray only at threshold, rotate to a different chemical group each time, and never spray on a fixed calendar (that also kills the natural enemies and flares other pests like whitefly and mites).

If fresh boreholes keep climbing after you spray, the worms may be resistant to that pyrethroid — switch to a different chemical group and tighten your scouting so you hit each new batch of eggs early. But if most of the bolls, pods and fruit are already bored and rotting, stop spraying — that yield is gone and more spray only wastes money and poison. Harvest whatever is still clean, then destroy and plough in all the crop residue to kill the worms hiding inside, and rotate to a non-host crop so they cannot carry over to next season.